The present invention relates generally to the dispensing of plastic fasteners of the type that are used, for example, to attach tags to articles of commerce and relates more particularly to a novel plastic fastener and a needle well-suited for use in dispensing said plastic fastener.
Plastic fasteners of the type comprising an elongated flexible filament having a first cross-bar at one end and a second cross-bar (or other enlargement, such as a paddle or a knob) at the opposite end are well-known and have been widely used in a variety of applications, such as in the attachment of merchandise tags to articles of commerce, in the attachment of buttons to garments, in the lasting of shoes, and in various packaging applications. Typically, such plastic fasteners are mass-produced by molding processes into either one of two different types of assemblies. One such assembly, an example of which is disclosed in U.S. Pat. No. 3,103,666, inventor Bone, issued Sep. 17, 1963 (which patent is incorporated herein by reference), is a clip-type assembly, said clip comprising a plurality of fasteners, each such fastener comprising a flexible filament having a first cross-bar at one end thereof and a paddle or second cross-bar at the opposite end thereof. The fasteners are arranged in a spaced, side-by-side orientation, with the respective first cross-bars parallel to one another and the respective paddles or second cross-bars parallel to one another, each of the first cross-bars being joined to a common, orthogonally-disposed runner bar by a severable connector. Adjacent second cross-bars or paddles also may be interconnected by severable connectors extending therebetween.
The aforementioned fastener clip is typically made by injection molding, the filament portions of the fasteners typically being stretched after molding to bring the filaments to their desired lengths and to strengthen the filaments by orienting the molecules therein along a common axis. Several commercial embodiments of the above-described fastener clip have been sold by the present assignee, Avery Dennison Corporation, as DENNISON.RTM.SWIFTACH.RTM.fastener clips.
A second type of fastener assembly, an example of which is disclosed in U.S. Pat. No. 4,533,076, inventor Bourque, issued Aug. 6, 1985 (which patent is incorporated herein by reference), is known as continuously connected fastener stock. In one type of continuously connected stock, the fasteners comprise a flexible filament having a cross-bar at one end thereof and a paddle (or second cross-bar) at the opposite end thereof, the respective cross-bars and paddles of successive fasteners being arranged end-to-end and being joined together by severable connectors. In another type of continuously connected fastener stock, the fastener stock is formed from two elongated and continuous side members coupled together by a plurality of equidistantly-spaced cross-links. Individual fasteners having an H-shape, often referred to as "plastic staples," are dispensed from the fastener stock by cutting the side members at appropriate points between crosslinks.
Continuously connected fastener stock is typically made by a rotary extrusion process of the type disclosed in U.S. Pat. No. 4,462,784, inventor Russell, which issued Jul. 31, 1984, and which is incorporated herein by reference. Said rotary extrusion process typically involves the use of a rotating molding wheel whose periphery is provided with molding cavities that are complementary in shape to the desired fastener stock. To form fasteners, plastic is extruded into the cavities of the molding wheel, and a knife in substantially elliptical contact with the wheel is used to skive the molded plastic from the molding wheel. Following molding, the filament portions of the fasteners are typically stretched to achieve their desired lengths and to strengthen the filaments.
Tools (often referred to as "tagging guns" or "fastener attaching tools") for dispensing individual fasteners from runner bar-containing clips or from continuously connected fastener stock above are known, examples of such tools being disclosed in the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. No. 4,039,078, inventor Bone, which issued Aug. 2, 1977; U.S. Pat. No. 5,433,366, inventors Deschenes et al., which issued Jul. 18, 1995; U.S. Pat. No. 4,121,487, inventor Bone, which issued Oct. 24, 1978; U.S. Pat. No. 5,320,269, inventors Deschenes et al., which issued Jun. 14, 1994; U.S. Pat. No. 4,955,475, inventors McCarthy et al., which issued Sept. 11, 1990; U.S. Pat. No. 4,456,161, inventor Russell, which issued Jun. 26, 1984; U.S. Pat. No. 5,024,365, inventor Bourque, which issued Jun. 18, 1991; and U.S. Pat. No. 4,998,661, inventors Deschenes et al., which issued Mar. 12, 1991.
Such tools typically comprise a needle, the needle typically including a stem portion. The stem portion typically is generally cylindrical in shape and has a tip adapted for insertion into an article of commerce. In addition, the stem portion has a longitudinal cylindrically-shaped bore adapted to receive the first cross-bar of a fastener. In addition, said stem portion also typically has a longitudinal slot adapted to permit the filament portion of a fastener to extend therethrough while the first cross-bar of the fastener is disposed in the longitudinal bore of the stem portion. During penetration of an article by the fastener cross-bar, the filament is bent rearwardly and approximately parallel to the longitudinal axis of the cross-bar, causing a rearwardly-facing bulge or arc of filament to extend from the cross-bar until the latter is ejected from the needle. As a result, another purpose served by the longitudinal slot of the needle is to receive the aforementioned rearwardly-facing bulge of filament and to keep said bulge from coming into contact with the article, where damaging stresses can be created on the filament and/or the article.
The needle also may include a base portion, said base portion being attached to the rear of the stem portion and being adapted to be removably received in the tool. The stem portion and the base portion may be a unitary structure or, as is more often the case, the base portion is insert molded onto the rear end of the stem portion.
Such tools also typically comprise an ejector rod for ejecting a first cross-bar from the needle and into the article of commerce and may also include a knife or similar severing means for cutting the severable connector between the first cross-bar being dispensed and its adjacent first cross-bar and feeding means for advancing the assembly of fasteners in the tool so as to align the forward most first cross-bar with the needle.
One problem that has been noted by the present inventors is that certain fasteners do not have a tensile strength that is as great as desired for certain applications. This problem is more familiar in the case of, but not exclusive to, plastic staples, which are typically made of polyurethane and typically have a tensile strength of about 1.2-1.4 pounds.